Bacteria communicate with each other by small auto-generated signal molecules, which are termed as auto inducers (AIs in brief). During the growth of bacterial quorum, these auto inducers are produced continuously and are subsequently secreted in the extracellular environment. When the concentration of the signal molecules reaches a threshold value, the expression of relevant genes in bacteria is initiated to adapt to the environmental changes. Such a regulatory system is termed as bacterial quorum sensing (QS) signal systems. QS enables unicellular bacteria to imitate multicellular organisms to accomplish some behaviors that cannot be accomplished when they are unicellular individuals.
In 1970, Nealson et al. discovered QS in V. fischeri for the first time, i.e. when bacteria reached a high population concentration, the bacteria generated bioluminescence. In deep study on V. fischeri, N-acyl homoserine lactones (AHL) synthesized from LuxI protein activate lux operon of V. fischeri by interaction with transcription activating factor luxR. Similar regulatory systems were found in many Gram-positive or Gram-negative bacteria. Their mechanism lies in that when bacteria are at a low population density, the auto inducers synthase gene is expressed at a basic level, resulting in a small amount of autoinduction signal molecules, which are diffused extracellularly and are diluted immediately in the surrounding environment. When the population density of bacteria increases gradually and reaches a threshold value, the autoinduction signal molecules will be permeated into cells and bind to transcriptional regulatory proteins to form a transcriptional regulatory protein-signal molecule polymer, which can bind to a specific DNA sequence of the signal molecule in chromosome to enable the expression of target genes including the synthetic gene of the signal molecule, also resulting in the production of more signal molecules. Such communication and transduction of information among bacteria has been proposed for a long time. However, systematic research is only conducted in the recent 10 years. Such a phenomenon has been demonstrated to be present in many bacteria. For example, chromobacterium violaceum has the same mechanism as V. fischeri, and can produce C6-HSL as an auto induction molecule, the receptor protein of which is CviR.
Bacterial quorum sensing enables the regulation of expression of some relevant genes in a population of bacteria, such as regulation of generation of antibiotics, bioluminescence, regulation of nitrogen-fixing gene, conjugal transfer of Ti plasmid, expression of virulent gene, pigment generation, bacterial swarming, formation of biofilms, and the like. In the late 1970s, scientists found that naturally occurring or artificially synthesized bacterial quorum-sensing regulators (including agonists or inhibitors) can interfere with the transduction of signaling system and regulate the expression of adverse gene in bacteria.
Bacterial quorum-sensing regulators do not interfere with normal physiological functions of cells in vivo, and thus are regarded as new direction for the development of antibacterials. Bacterial quorum-sensing inhibitors can be used in combination with antibiotics to enhance sensitivity of pathogenic bacteria to antibiotics, and can be used to treat a disease (including, but not limited to peritonitis, cholecystitis, cystitis, diarrhea, endocarditis, gastroenteritis, pyothorax, sepsis and other various diseases) caused by a Gram-negative bacterium including, but not limited to E. coli, Bacillus proteus, Bacillus dysenteriae, Bacillus pneumoniae, Brucella, Haemophilus influenzae, Hemophilus parainfluenzae, Moraxella catarrhalis, Acinetobacter, Yersinia, legionella pneumophila, Bordetella pertussis, Bordetella parapertussis, Shigella spp., Pasteurella, Vibrio cholerae, and Vibrio Parahemolyticus, particularly, to treat a disease caused by drug-resistant Gram-negative bacteria not sensitive to current antibiotics.
The purpose of the invention is to synthesize new bacterial quorum-sensing regulator, for use in the treatment of a disease caused by a Gram-negative bacterium, particularly a disease caused by drug-resistant Gram-negative bacteria.